1. Field of the Invention
This invention relates generally to methods of making wire drawing dies, and more particularly to a method of making a wire drawing die employing a hard, wear-resistant material. This application is related to and is an improvement on U.S. Application Ser. No. 841,886, now U.S. Pat. No. 4,144,739.
2. Description of the Prior Art
Natural diamond wire drawing dies have been manufactured for many years and typically comprise a metal casing in which the diamond is mounted, the casing in turn being adapted to be mounted in a wire drawing machine. U.S. Pat. No. 2,171,323 discloses one prior method of making a natural diamond wire drawing die.
Polycrystalline aggregates of synthetic diamond have recently become available and an annular sintered tungsten carbide blank having a core of polycrystalline aggregate of synthetic diamond is sold by the General Electric Company under the trademark "Compax". In the past, wire drawing dies employing blanks having polycrystalline aggregate of synthetic diamond cores have been shrink-fitted in a cavity in the casing; however, such shrink-fitting of the blank has required a substantial amount of skilled labor and has resulted in excessive breakage of the synthetic diamond core. A plug is shrink-fitted in the casing cavity over the blank and has the usual countersunk opening formed therethrough to the core; however, during the process of machining, the countersunk opening may extend to the outside diameter of the plug and into the surrounding casing.
The General Electric Company has even more recently introduced another synthetic hard, wear-resistant material which may be suitable for wire drawing dies, polycrystalline cubic boron nitride, referred to by the trademark "Borazon". Polycrystalline aggregate of natural diamond may also be suitable for wire drawing dies.
It is therefore desirable to provide a wire drawing die employing a hard, wear-resistant material, such as polycrystalline aggregate of synthetic or natural diamond or polycrystalline cubic boron nitride, and a method of making the same which eliminates prior problems involved in shrink-fitting of the blank in the casing, reduces breakage in the core, and eliminates the problem of the countersunk opening in the plug extending into the casing.